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I checked into that very subject recently (Meaning Bonneville)...saw the 175cc class record was around 130-136mph....something like that. I'm at about 25 rear wheel hp at 209cc. Not sure of the rule specifics...if 175cc class means NO MORE than 175cc.

When I looked at the numbers it seemed possible to me. In road race trim with a full fairing, level road, no headwind I think I could get 100+ out of my bike in road race trim.

Fully streamlined, fully tuned for max hp at max rpm (no worries about midrange etc), skinny tires, etc etc....I think I could get 130mph out of my engine as it sits now (209cc). It would be a challenge at 175cc....but I think close enough of a possibility that it would be a lot of fun to try.

I'd be happy to offer any technical assistance I can. A couple of months ago I even mentioned to the wife how much fun it would be to try for a land speed record with a 175...just too far away for us.

As a base line...my bike routinely hits 88-90mph on the straight at NHIS...with no fairing, 200+ lb rider and road race gearing. It will pull around 95+ mph on faster tracks.

I think you'd be looking at around $6-8,000 for a serious effort though.
JohnnyB
 

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Biggest expense would probably be for bodywork, wheels and engine. For a serious effort you are looking at a couple of thousand in engine work.
Remember you need both lots of hp and lots of rpm. Highly ported head by a professional with suitable valve train work would be about $1000. If the cc limit is really 175 then you maybe use OEM pistons..although the lack of high compression will be a problem. Basically you'll want to be able to spin this thing to the moon....12,000-13,000 rpm. You'll want a PVL ignition, 26mm carbs, I'd go with a cam similar to what I use now...or better yet have a good cam grinder work you up something that makes good high rpm power but isn't too abusive to the valve train at high rpm. (medium lift, large overlap, gentle ramps if possible?). Exhaust would be fairly short and fat.
Wheels would probably be 18" WM1...alloy, with small disk if allowed...not sure about tire availability...but 130mph is not hugely fast so super exotic tires probably wouldn't be necessary.

Streamlining would be the huge factor...and an engine that can wind up the kind of rpm you need and not come apart....meaning valve train work...stiff springs, light valves (Ti would be great), bronze guides, maybe run no seals to reduce friction. Unlike a RR engine you'd need an engine that could run at redline for minutes at a time. Full streamliner body would probably be an absolute necessity...but that will put you in a particular class. I can't imagine any 175 Honda in any form being able to top 110mph without a streamliner body.

If there was a 175 speed record effort local to me I'd be in on it like white on rice. I think it would be a freakin blast to do.
JohnnyB
 

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That have various classes for four strokes, two strokes, vintage etc. The rule book will have all that crap. Land Speed records probably have ten times as many classes as any other type of racing.
JohnnyB


PS. But...as the present record shows...the record for 175cc is something like 136mph....and I think you could get a vintage Honda 175 twin very very close to that in the right body work. So either people aren't trying with two strokes...or they just don't offer much of an advantage in top speed.


Edited by - jbranson on Dec 26 2006 12:03:47 AM
 

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I was talking to Champ the other day about USCRA Speed Run competition. Would be cool if we could rent a 1/2 to 1 mile runway somewhere and take our vintage bikes out for a top speed competition.

I'd love that...and it would give me all kinds of tuning data about fairings, gearing, and tuning an engine for top speed. Would seem kind of a cheap easy thing to setup too.

JohnnyB
 
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